Fig. 1.
Nitric oxide protects against β-amyloid-induced death in neuronal cells. A, Aβ1–42induces dose-dependent death in three different neuronal cell types. E18 hippocampal neurons were grown in culture for 3 d and then exposed to increasing concentrations of Aβ1–42. Survival was assessed after 1 d by counting nuclei in cell lysates (n = 3). Survival is reported relative to untreated cultures and is given as mean ± SEM. Sympathetic neurons were grown in culture for 5 d and then exposed to increasing concentrations of Aβ1–42. Survival was assessed after 1 d by counting cells in the living cultures. Survival is reported relative to that in the same cultures before Aβ1–42treatment and is given as mean ± SEM (n = 3). PC12 cells were exposed to increasing concentrations of Aβ1–42. Survival was assessed after 1 d by counting nuclei in cell lysates (n = 3). Survival is reported relative to untreated cultures and is given as mean ± SEM. These are representative experiments. Comparable results were obtained in six additional independent experiments with hippocampal neurons, in three additional experiments with sympathetic neurons, and in five additional experiments with PC12 cells. B, Mn-SOD is not induced by Aβ1–42 treatment. PC12 cells were treated with or without Aβ1–42 (10 μm) for 6 hr (n = 3). Cells were extracted with 0.5% NP-40, and protein was measured by the Bradford method. Total SOD and Mn-SOD levels were determined by the xanthine–xanthine oxidase system, with measurement of the reduction of nitroblue tetrazolium at 560 nm in the presence and absence of KCN. Mn-SOD activity was determined from an SOD standard curve and is reported as the KCN-insensitive activity ± SEM. C, Increasing NO protects from Aβ1–42-induced neuronal cell death. PC12 cells and sympathetic neurons were exposed to Aβ1–42 (10 μm) in the presence or absence of SNAP (100 μm) or l-NAME (10 μm). Survival was assessed after 1 d as described above (n = 3). This is a representative experiment; comparable results were obtained in three additional independent experiments. Survival is reported relative to untreated cultures and is given as mean ± SEM. Similar results were obtained with cultured sympathetic neurons.